Menu conflict with RT-Theme 10

Hi!

I have installed the Post Types Order (PTO) plugin with RT-Theme 10. This enabled me to re-order the products on my site manually like I needed to do – so far so good.

However, that plugin has introduced a problem with disappearing left-hand menu on the product category pages used by RT Theme 10:

– When I click on a product category, the left hand menu disappears.
– The products are still listed, so I can click on a product thumbnail and move on to a product page.
– When the product page opens, the menu appears again and works fine.

Disabling the PTO plugin makes the menu work again.

So: there is evidently some sort of conflict between the category pages of this theme, and the PTO plugin.

The Products page in question is located here:
https://www.combutech.se/produkter/

The last 5 sub-menu items under the Products page are Categories (the first one is a static page). And as you can see, clicking on any one of those categories causes the menu to disappear, such as here:
https://www.combutech.se/products/kompletta-toalettsystem/

(It also seems like load speed has increased somewhat after installing the PTO plugin, but that’s another story.)

FYI: I have tried deactivating ALL other plugins on the site, but that did not resolve the problem.

https://www.ads-software.com/extend/plugins/post-types-order/